The invention relates to a method for regulating a charge air pressure of an internal combustion engine of a vehicle having an exhaust gas turbocharger, a fresh gas supply device, a vehicle air system with an air conditioning system and with a compressor, which can be supercharged by the exhaust gas turbocharger, and an engine control unit, as well as corresponding devices.
An internal combustion engine having an exhaust gas turbocharger has, in certain operating states, in particular when there is a torque request, phases of insufficient air supply by the exhaust gas turbocharger with compressed fresh air, as a result of which what is referred to as turbo lag is produced. In order to eliminate this turbo lag the increased air demand is covered by a fresh gas supply device by means of an additional fresh air supply. This additional fresh air can be obtained, for example, from a compressed air accumulator of a vehicle air system. This requires the associated compressor to be configured to supply compressed air for this increased demand. Such a compressor can be supercharged, that is to say it can use compressed air from the exhaust gas turbocharger.
It is considered a disadvantage here that compressed air is extracted from the internal combustion engine in the direction of flow downstream of the exhaust gas turbocharger irrespective of whether or not the internal combustion engine is currently at an operating point at which it requires the fresh air compressed by the exhaust gas turbocharger. This can lead to unacceptable dips in power.
Compressors are mainly driven mechanically. The advantage of what is referred to as a clutch compressor has only become a current issue again in the last few years as fuel prices have continuously risen. Continuously supercharged compressors are also the state of the art, in particular in the USA. For example, DE 102008004807A1 discloses a supercharged clutch compressor.
Electronically regulated air conditioning systems are also state of the art and are installed on a series basis in utility vehicles which are braked using compressed air. A fresh gas supply device is known, for example, from WO2006/089779A1. All the systems in themselves provide advantages with respect to saving fuel, emissions and/or the transient performance capability of a vehicle. However, the overall potential taking into account the requirements of the internal combustion engine with an exhaust gas turbocharger are not implemented.
The object of the invention is therefore to make available improved methods for regulating the charge air pressure of an internal combustion engine of a vehicle having an exhaust gas turbocharger, wherein the above disadvantages are overcome or significantly reduced, and further advantages are provided. A further task of the invention is to specify corresponding devices.
An inventive idea consists in the fact that when there is a torque request to the internal combustion engine, the charge air pressure is regulated by suspending supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor, as a result of which the charge air pressure quickly rises to a setpoint value, and the turbo lag is considerably reduced. Excellent acceleration values together with at the same time optimum consumption values are obtained.
This permits the following advantages to be implemented:
(1) maximum feeding of air by the compressor in the supercharged state, in particular in over-run phases or braking phases of the vehicle, in order to supply or fill the vehicle air system with air,
(2) maximum feeding of air by the compressor in the supercharged state, in particular in phases in which the internal combustion engine does not require the maximum quantity of fresh air and an excessively high charge pressure is present (for example partial load or waste gate phase), in order to fill the vehicle air system.
Accordingly, a first method for regulating a charge air pressure of an internal combustion engine of a vehicle having an exhaust gas turbocharger, a fresh gas supply device, a vehicle air system with an air conditioning system and with a compressor, which can be supercharged by the exhaust gas turbocharger, and an engine control unit, has the following method steps:
(1) registering of a torque request to the internal combustion engine, the determination of a current charge air pressure and the determination of a current pressure of the vehicle air system;
(2) comparison of the current charge air pressure with a setpoint charge air pressure which corresponds to this torque request, and
(3) comparison of the determined, current pressure of the vehicle air system with a setpoint operating pressure of the vehicle air system; and
(4) regulation of the charge air pressure by suspending the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure and the current pressure of the vehicle air system is higher than or equal to the setpoint operating pressure of the vehicle air system.
This provides an intelligent method of regulating the engine control system, electronic air conditioning system and supercharged compressor, as a result of which, on the one hand, the additional air demand is covered by a fresh gas supply device. On other hand, the disadvantages relating to the performance of an internal combustion engine with an exhaust gas turbocharger are avoided.
Phases in which the internal combustion engine requires, for example, the maximum fresh air supply of the exhaust gas turbocharger when there is a torque request, for example when an accelerator pedal is activated, are detected by the engine control unit, and said engine control unit detects the associated, current charge air pressure which is compared with a setpoint value in order, for example, to generate a signal when the charge air pressure is too low. The signal is supplied to the air conditioning system, which decides, on the basis of the current pressure level of the vehicle air system, whether the compressor has to feed compressed air in this phase. If this pressure of the vehicle air system is sufficient, the supply of compressed air by the exhaust gas turbocharger to the compressor is suspended, for example by switching off the compressor. This occurs in a compressor with an electric drive by virtue of the fact that the electric drive is switched off. If the compressor is connected to the internal combustion engine via a shiftable clutch device, the shiftable clutch device can be disengaged. It is also conceivable to combine the two types of drive and others.
This ensures that the charge air pressure is quickly built up at the inlet manifold or intake manifold of the internal combustion engine since no compressed air is branched off for the compressor which is switched off. The compressor is not switched on again or enabled for switching on until the torque request is ended.
The compressor can be switched off by the engine control unit, the air conditioning system and/or a compressor system control device.
Furthermore, a second method for regulating a charge air pressure of an internal combustion engine of a vehicle having an exhaust gas turbocharger, a fresh gas supply device, a vehicle air system with an air conditioning system and with a compressor and an engine control unit, wherein the compressor is supplied with compressed air from the exhaust gas turbocharger or with air from at least one further air source, has the following method steps:
(1) registering of a torque request to the internal combustion engine, the determination of a current charge air pressure and the determination of a current pressure of the vehicle air system;
(2) comparison of the current charge air pressure with a setpoint charge air pressure which corresponds to this torque request, and
(3) comparison of the determined, current pressure of the vehicle air system with a setpoint operating pressure of the vehicle air system; and
(4) regulation of the charge air pressure by suspending the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure and the current pressure of the vehicle air system is higher than or equal to the setpoint operating pressure of the vehicle air system, or by suspending the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor and supplying air to the compressor from at least one further air source if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure, and the current pressure of the vehicle air system is lower than the setpoint operating pressure of the vehicle air system.
Significant advantages here are that not only is the compressor switched off if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure and the current pressure of the vehicle air system is higher than or equal to the setpoint operating pressure of the vehicle air system, in order to suspend the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor (as explained in more detail above), but also that even in a possible extreme case, when it is absolutely necessary for the vehicle air system to be filled during the phase of torque request, that is to say for the compressor to operate, the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor is suspended and the compressor continues to feed at the same time. This can be made possible by virtue of the fact that in such a case the compressor is connected to the at least one further air source by switching over at least one valve. In this context, a connection of the compressor inlet to the compressor of the exhaust gas turbocharger is, for example, closed off by a valve and the compressor inlet is connected to a further air source, for example the ambient air, by a further valve. In this case, the compressor does not operate in a supercharged state but it can nevertheless generate the necessary compressed air, and at the same time the charge air pressure is regulated in an optimum way.
The comparison of the charge air pressures can be carried out by the engine control unit. It generates, for example, a signal if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure, in which case the generated signal is conducted to the air conditioning system which then carries out the compression of the determined, current pressure of the vehicle air system with the setpoint operating pressure of the vehicle air system. However, it is also possible for the air conditioning system to carry out the comparison of the charge air pressures. An additional control unit can also be used for this purpose, many combinations being conceivable in this context.
Furthermore, there is provision for the suspension of the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor to be carried out by the engine control unit, the air conditioning system and/or a compressor system control device. Further combinations are also possible here.
A device for regulating a charge air pressure of an internal combustion engine of a vehicle comprises: an exhaust gas turbocharger for generating compressed charge air; a fresh gas supply device for supplying the compressed charge air and additional fresh gas to the internal combustion engine; a vehicle air system having an air conditioning system, wherein the air conditioning system is provided for controlling the vehicle air system and for determining a current pressure of the vehicle air system; a compressor for generating compressed air for the vehicle air system, wherein the compressor is connected to the exhaust gas turbocharger in order to supply compressed charge air to the compressor; and an engine control unit for controlling the internal combustion engine, for registering a torque request to the internal combustion engine in order to determine a current charge air pressure, wherein the engine control unit is designed to compare the current charge air pressure with a setpoint charge air pressure which corresponds to this torque request, and to generate a signal if the current charge air pressure is lower than the setpoint charge air pressure, and to pass on this signal to the air conditioning system, and wherein the air conditioning system and/or the engine control unit are/is designed to compare the determined, current pressure of the vehicle air system with a setpoint operating pressure of the vehicle air system) and to regulate the charge air pressure by suspending the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure and the current pressure of the vehicle air system is higher than or equal to the setpoint operating pressure of the vehicle air system.
This device is particularly suitable for carrying out the first method explained above.
A further device for regulating a charge air pressure of an internal combustion engine of a vehicle is made available and is provided with an exhaust gas turbocharger for generating compressed charge air; a fresh gas supply device for supplying the compressed charge air and additional fresh gas to the internal combustion engine; a vehicle air system having an air conditioning system, wherein the air conditioning system is provided for controlling the vehicle air system and for determining a current pressure of the vehicle air system; a compressor for generating compressed air for the vehicle air system, wherein the compressor can be connected to the exhaust gas turbocharger in order to supply compressed charge air to the compressor, and in order to supply charge air from at least one further air source; and an engine control unit for controlling the internal combustion engine and for registering a torque request to the internal combustion engine, wherein the engine control unit is designed to compare the current charge air pressure with a setpoint charge air pressure which corresponds to this torque request, and to generate a signal if the current charge air pressure is lower than the setpoint charge air pressure, and to pass on this signal to the air conditioning system, and wherein the air conditioning system and/or the engine control unit are/is designed to compare the determined, current pressure of the vehicle air system with a setpoint operating pressure of the vehicle air system and to regulate the charge air pressure by suspending the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure, and the current pressure of the vehicle air system is higher than or equal to the setpoint operating pressure of the vehicle air system, and by suspending the supply of compressed air, supplied by the exhaust gas turbocharger, to the compressor and supplying air to the compressor from at least one further air source if the determined, current charge air pressure is lower than the corresponding setpoint charge air pressure, and the current pressure of the vehicle air system is lower than the setpoint operating pressure of the vehicle air system.
This device is particularly suitable for carrying out the second method explained above.
There is provision that the compressor can be connected to the at least one further air source via an intake air valve, and can be connected to the exhaust gas turbocharger via a charge air valve. The further air source can be, for example, the ambient air and/or air from a further exhaust gas turbocharger or another air compressor device.
The device can have a bus device for connecting the engine control unit, the air conditioning system, the fresh gas supply device and a compressor system control device. This bus device may be, for example, a CAN bus which is already present or a separate bus.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.